A new research study has found a potential link between U.S. counties with a history of slavery and slower rates of decline in heart disease mortality. The researchers found that while heart disease has decreased by approximately 60 percent in the last 50 years nationwide, the pace of decline was slower for blacks compared to whites and slower in counties with more compared to less slaveholding in 1860.

The research, by Michael Kramer, PhD, associate professor of epidemiology at the Emory Rollins School of Public Health and colleagues, was published in the journal SSM – Population Health.

As part of the study, the research team analyzed rates of heart disease mortality stratified by race between 1968 and 2014 from southern U.S. counties in states permitting slavery before the Civil War. Using spatial analysis and Bayesian methods, the researchers compared Census figures with socioeconomic data to determine what affects geography and history have had on current health outcomes for populations in the South.

"A challenge for public health professionals is understanding the reasons for racial and geographic differences in the pace of progress in fighting heart disease," says Kramer. "Building on work by historians and sociologists suggesting the legacy of slavery persists today in the local institutions and norms of southern counties – enlarging racial disparities in educational attainment, poverty and employment – we wondered whether this legacy also impacts the rate of decline in heart disease mortality."

The group first measured the association between slave concentration in 1860 and declines in heart disease mortality controlling only for differences in land use and population size. Then, they considered the degree to which racial gaps in educational attainment and economic opportunity might account for the association. Educational attainment was measured by studying disparities in illiteracy among blacks and whites in 1930 and college attainment in 1970. Economic opportunity included variables for black–white disparities in unemployment and median home values in 1930 and poverty rates in 1970. A legacy of higher slave concentrations was strongly associated with slower declines in heart disease, particularly for blacks, and this was partly explained by the racial gaps in education and economic opportunity.

The slower decline in heart disease mortality in these counties is consistent with (but not proof of) the idea that places are more or less unequal, and that degree to which they are unequal may be contributing to the ability of today's communities to benefit from new health information, new knowledge, and the diffusion of technology and progress to address heart disease, Kramer notes.

"Public health action needs to go beyond simple individual messaging around heart health and engage with the historical legacy of places and their institutions to identify barriers to future progress," says Kramer.